I have been making pneumatic cannons for quite a while, mostly for shooting golf balls, stones and that sort of projectile. The cannons have been quite successful but the need to pump up etc. for only one shot has begun to annoy me.

What I really want to build at the moment is a tennis ball launcher, that is very quick to load, decently powerful, cheap to build/run and easy to use.

Having no experience in the combustion/hybrid area, what can you guys recommend me? I am interested in the best system to use (pure combustion v. hybrid), the best and cheapest fuel to use, the quickest loading systems and all the fuel ratio stuff that I don't know much about. Please tell me of any ideas you have and point me to any past builds of yours.

I can get a pc fan easily so will do that. Should I put it in the centre of the chamber? And should I run it during combustion or only up until (and after for clearance)?

ratios... I presume that 2:1 is in terms of volume? Is it better to have a thicker pipe for the chamber? Lots of people seem to use a 4" pipe and a 2.5"(tennis ball) barrel.

Carb cleaner - Is it cheap? It seems everyone is using propane - thoughts on that?

Also I was wondering what the deal is in terms of knowing when your gas to air solution is at the right ratio. Do people use a measured injector, if so how does the system work? (couldn't find a related forum post).

frigaardj wrote:Carb cleaner - Is it cheap? It seems everyone is using propane - thoughts on that?

Don't use carb cleaner. Just use propane and do a little reading on here to find a setup that makes sense to you.

Using carb cleaner, while having all the information available on spudfiles at your access would be like using a chisel and slate to send a message via pterodactyl when you could just send a text message...